A cubic spinel-structured sulfide composite gas-sensitive material, a gas-sensitive sensor, its preparation method and application

Abstract

This invention discloses a cubic spinel-structured sulfide composite gas-sensitive material, a gas sensor, its preparation method, and its application, belonging to the field of gas sensor technology. The preparation method of this composite gas-sensitive material involves using FeCl2, CdCl2, and InCl3 as metal sources, and thiourea as a sulfur source, placing them together in a solvent of water, adding citric acid or sodium citrate as a dispersant, and obtaining a precursor material through a hydrothermal reaction. After calcination and annealing, a cubic spinel-structured FeIn2S4 / CdIn2S4 heterojunction material powder is obtained. The two gold electrodes and the ceramic tube of the gas sensor are coated with the cubic spinel-structured sulfide composite gas-sensitive material. The gas sensor based on this invention, made from a cubic spinel-structured sulfide composite gas-sensitive material, has a simple manufacturing process, low production cost, and is suitable for industrial mass production. It has broad application prospects in the field of acetone detection in trace hazardous situations.

Description

Technical Field

[0001] This invention belongs to the field of gas sensor technology, specifically relating to a cubic spinel structure sulfide composite gas-sensitive material, a gas-sensitive sensor, its preparation method, and its application. Background Technology

[0002] With industrial development and technological advancements, organic compounds are increasingly widely used in industrial and biomedical fields. Acetone, as a good solvent and raw material for organic synthesis, is of great significance for industrial safety and environmental protection in its detection. When the acetone concentration exceeds 450 mg / m³... 3 At concentrations of 173 ppm, acetone is easily volatilized and can irritate the eyes, nose, and central nervous system. In breath diagnoses, acetone is a typical biomarker for diabetes. The acetone concentration in the breath of healthy individuals is often below 0.8 ppm, while that of diabetic patients is generally above 1.8 ppm. Using the acetone concentration in exhaled breath to assist in determining whether a patient has diabetes is a good non-destructive testing method. However, metal oxide-based sensors typically suffer from high operating temperatures, poor detection limits, and slow response times, limiting their practical applications. Transition metal sulfides, with their large specific surface area, suitable band gap, and good conductivity at room temperature, are promising candidate materials for low-temperature gas sensors. Furthermore, compared to monometallic sulfides, bimetallic sulfides are attracting increasing attention due to their tunable band structure, crystal structure, electronic structure, and controllable physicochemical properties. In addition, their abundant redox active sites, bimetallic synergistic effects, and ion diffusion channels make them potential sensing materials.

[0003] Chinese patent CN113899790A discloses an acetone sensor, its preparation method, and its application. The acetone sensor is prepared using spinel MFe2O4 (M = Zn and Cu) microspheres with a multi-cavity structure. When M = Zn and Cu, the response values ​​of ZnFe2O4 and CuFe2O4 to 100ppm acetone are 25 and 8.6, respectively, and the optimal operating temperatures are 250℃ and 200℃, respectively. The high operating temperature of the sensor has a significant impact on stability and poor safety.

[0004] Chinese patent CN120064406A discloses a gas sensor based on defective metal-organic framework materials, its preparation method, and its application. The gas sensor uniformly disperses defective MOF materials with highly active sites in a solution and coats them onto interdigitated electrodes using a drop-coating method to form a flat and stable gas-sensitive film, thereby obtaining the gas sensor. However, the gas sensor has too low responsiveness to acetone gas, which may cause misjudgment under similar conditions. Summary of the Invention

[0005] To address the problems existing in the prior art, the present invention aims to provide a cubic spinel structured sulfide composite gas-sensitive material and its preparation method. This sulfide composite gas-sensitive material is used to prepare an acetone sensor, and the resulting acetone sensor is applied to acetone gas detection, which can accurately detect acetone gas at a relatively low operating temperature.

[0006] The objective of this invention is achieved through the following technical solution:

[0007] This invention provides a method for preparing a cubic spinel structured sulfide composite gas-sensitive material. FeCl2, CdCl2 and InCl3 are used as metal sources, and thiourea is used as a sulfur source. They are placed together in a solvent water, and citric acid or sodium citrate is added as a dispersant. The precursor material is obtained through a hydrothermal reaction, and after calcination, it is annealed to obtain spinel structured FeIn2S4 / CdIn2S4 heterojunction powder.

[0008] Furthermore, the preparation method of the cubic spinel structured sulfide composite gas-sensitive material specifically includes the following steps:

[0009] (1) Dissolve FeCl2, CdCl2, InCl3, thiourea and dispersant in water, stir to dissolve, and obtain a solution;

[0010] (2) The solution obtained in step (1) is transferred to a high-pressure reactor and heated to carry out a hydrothermal reaction. After the reaction is completed, it is naturally cooled to room temperature, washed, and dried at a constant temperature to obtain a red precursor material.

[0011] (3) The red precursor material was placed in a heating furnace for calcination. After calcination, it was cooled to room temperature with the furnace to obtain cubic spinel structure FeIn2S4 / CdIn2S4 heterojunction material powder.

[0012] Furthermore, in step (1), the molar ratio of FeCl2, CdCl2, InCl3, thiourea and dispersant is (0.05-0.45):(0.05-0.45):(1-1.35):(2.5-5):(1-2), and magnetic stirring is used with a rotor speed of 450rpm-550rpm for 20min-40min.

[0013] Furthermore, in step (2), the hydrothermal reaction temperature is 180℃-200℃ and the time is 20h-24h; the drying temperature is 40℃-60℃ and the time is 12h-24h.

[0014] Furthermore, in step (3), the calcination temperature is 250℃-350℃, the heating rate is 2℃ / min-4℃ / min, and the calcination time is 1h-3h.

[0015] The present invention also provides a cubic spinel structured sulfide composite gas-sensitive material, which is prepared by the preparation method of the cubic spinel structured sulfide composite gas-sensitive material.

[0016] The present invention also provides a gas sensor based on a cubic spinel structure sulfide composite gas-sensitive material, which adopts a side-heated structure and consists of two parallel annular gold electrodes, a ceramic tube, a conductive wire, a heating resistance wire and an electrode base. The two gold electrodes and the ceramic tube are coated with the cubic spinel structure sulfide composite gas-sensitive material.

[0017] This invention also provides a method for preparing a gas sensor based on a cubic spinel structure sulfide composite gas-sensitive material, specifically including the following steps:

[0018] (1) Take an Al2O3 ceramic tube and fix it at the center of the hexagonal electrode base. The surface of the Al2O3 ceramic tube is covered with two discrete parallel gold electrodes. Each gold electrode is connected to a platinum conductive wire at both ends. The other ends of the four platinum conductive wires are connected to the four electrodes corresponding to the hexagonal electrode base. The nickel-chromium alloy resistance wire passes through the inside of the ceramic tube. The two ends of the nickel-chromium alloy resistance wire are connected to the two electrodes of the hexagonal electrode base opposite to the end face of the ceramic tube.

[0019] (2) The cubic spinel structure FeIn2S4 / CdIn2S4 heterojunction material powder is added to anhydrous ethanol to form a suspension, and the ceramic tube surface and gold electrode of step (1) are coated to make the gold electrode completely covered by the suspension.

[0020] (3) The sensor obtained in step (2) is subjected to heating and aging treatment to obtain a semiconductor gas sensor based on cubic spinel structure sulfide composite gas-sensitive material.

[0021] Further, in step (1), the inner diameter of the Al2O3 ceramic tube is 0.6mm-0.8mm, the outer diameter is 1.0mm-1.3mm, and the length is 4.0mm-5.0mm;

[0022] The width of each ring-shaped gold electrode is 0.4mm-0.5mm, and the spacing between two ring-shaped gold electrodes is 0.5mm-0.6mm;

[0023] The length of each platinum conductive wire is 4mm-5mm;

[0024] Step (2) The mass-to-volume ratio of cubic spinel FeIn2S4 / CdIn2S4 heterojunction material powder to anhydrous ethanol is (50-60) mg:(60-80) μL;

[0025] Step (3) The temperature for heating and aging is 100℃-200℃, and the aging time is 2-4 days.

[0026] The present invention also provides an application of a gas sensor based on a cubic spinel structure sulfide composite gas-sensitive material for the accurate monitoring of trace amounts of acetone gas at a relatively low temperature of 100°C.

[0027] This invention relates to a gas sensor based on a cubic spinel structure sulfide composite gas-sensitive material for detecting acetone gas. The working principle is as follows:

[0028] For gas sensors based on cubic spinel-structured sulfide composite gas-sensitive materials, the appropriate FeIn2S4 / CdIn2S4 heterojunction ratio is crucial to their gas-sensing performance. According to Wolkenstein's model, at different ambient temperatures, adsorbed O2 molecules partially ionize by capturing electrons from the sensing semiconductor surface. O 2- , O - and O 2 - Because FeIn₂S₄ and CdIn₂S₄ have similar crystal structures, they not only form heterostructures, but also exhibit cross-substitution of Fe and Cd in the S-Cd-S and S-Fe-S structures. Since the bond lengths of Fe-S and Cd-S are different, their surface energies also differ, leading to different gas adsorption properties. Furthermore, structural changes create numerous defect sites. The increased number of defect sites and the formation of heterojunctions on the material surface result in greater oxygen adsorption, leading to a thicker electron depletion layer (EDL). This significantly increases the sensor's resistance. When the sensor is exposed to acetone gas, the oxygen anodes adsorbed on the sensor undergo a redox reaction, transferring a large number of electrons back to the material's internal conduction band, resulting in a significant decrease in sensor resistance. The change in sensor resistance is used to detect the gas signal. The uniform spherical structure also provides a higher specific surface area, further facilitating gas adsorption.

[0029] Advantages and effects of the present invention:

[0030] 1. The present invention prepares FeIn2S4 / CdIn2S4 sulfide heterojunction nanospheres by a one-step hydrothermal method and a subsequent low-temperature calcination strategy. The synthesis method is simple and the synthesis cost is low.

[0031] 2. The FeIn2S4 / CdIn2S4 sulfide heterojunction nanospheres prepared by the present invention through a one-step hydrothermal method and subsequent low-temperature calcination strategy provide an effective sensitive material for the development of a high-performance cubic spinel acetone gas sensor.

[0032] 3. FeIn2S4 and CdIn2S4 have similar crystal structures and similar morphologies were formed through a one-step hydrothermal method. The FeIn2S4 / CdIn2S4 heterojunction material synthesized by the one-step hydrothermal method significantly improved electron flow and enhanced the gas-sensing characteristics of the sensor for acetone. Moreover, the bimetallic sulfide material has a lower operating temperature for acetone gas. It is evident that the gas sensor of FeIn2S4 / CdIn2S4 sulfide heterojunction nanosphere material has broad application prospects in the field of acetone detection in trace hazardous situations.

[0033] 4. The gas sensor based on cubic spinel structure sulfide composite gas-sensitive material of the present invention has a simple manufacturing process, low preparation cost, and is suitable for mass production in industry. Attached Figure Description

[0034] Figure 1 The XRD diffraction patterns of the material powders prepared in Examples 1 to 5 and Comparative Examples 1 to 2 are shown.

[0035] Figure 2 The image shows the scanning electron microscope (SEM) morphology of the powder material prepared in Example 1.

[0036] Figure 3 The image shows the scanning electron microscope (SEM) morphology of the powder material prepared in Example 2.

[0037] Figure 4 The image shows the scanning electron microscope (SEM) morphology of the powder material prepared in Example 3.

[0038] Figure 5 The image shows the scanning electron microscope (SEM) morphology of the powder material prepared in Example 4.

[0039] Figure 6 The image shows the scanning electron microscope (SEM) morphology of the powder material prepared in Example 5.

[0040] Figure 7 The image shows the scanning electron microscope (SEM) morphology of the material powder prepared in Comparative Example 1.

[0041] Figure 8 The image shows the scanning electron microscope (SEM) morphology of the powder material prepared in Comparative Example 2.

[0042] Figure 9 The gas sensors prepared in Examples 1 to 5 and Comparative Examples 1 to 2 are shown to respond to 100 ppm acetone gas at different temperatures.

[0043] Figure 10 The response curves of the gas sensor prepared in Example 1 to different concentrations of acetone gas at the optimal operating temperature of 100°C are shown.

[0044] Figure 11 The response curves of the gas sensor prepared in Example 2 to different concentrations of acetone gas at the optimal operating temperature of 100°C are shown.

[0045] Figure 12 The response curves of the gas sensor prepared in Example 3 to different concentrations of acetone gas at the optimal operating temperature of 100°C are shown.

[0046] Figure 13 The response curves of the gas sensor prepared in Example 4 to different concentrations of acetone gas at the optimal operating temperature of 100°C are shown.

[0047] Figure 14 The response curves of the gas sensor prepared in Example 5 to different concentrations of acetone gas at the optimal operating temperature of 100°C are shown.

[0048] Figure 15 The response curves of the gas sensor prepared for Comparative Example 1 to different concentrations of acetone gas at the optimal operating temperature of 100℃.

[0049] Figure 16 The response curves of the gas sensor prepared in Comparative Example 2 to different concentrations of acetone gas at the optimal operating temperature of 100℃ are shown.

[0050] Figure 17 This is a continuous measurement curve of 100 ppm acetone gas by the gas sensor prepared in Example 1 at the optimal operating temperature of 100°C.

[0051] Figure 18 This is a continuous measurement curve of 100 ppm acetone gas by the gas sensor prepared in Example 2 at the optimal operating temperature of 100°C.

[0052] Figure 19 This is a continuous measurement curve of 100 ppm acetone gas by the gas sensor prepared in Example 3 at the optimal operating temperature of 100°C.

[0053] Figure 20 This is a continuous measurement curve of 100 ppm acetone gas by the gas sensor prepared in Example 4 at the optimal operating temperature of 100°C.

[0054] Figure 21 The continuous measurement curve of 100 ppm acetone gas by the gas sensor prepared in Example 5 at the optimal operating temperature of 100°C;

[0055] Figure 22 The continuous measurement curve of 100 ppm acetone gas by the gas sensor prepared in Comparative Example 1 at the optimal operating temperature of 100℃ is shown.

[0056] Figure 23 The continuous measurement curve of 100 ppm acetone gas by the gas sensor prepared in Comparative Example 2 at the optimal operating temperature of 100℃ is shown.

[0057] Figure 24 The graph shows the response values ​​of the gas sensors prepared in Examples 1 to 5 and Comparative Examples 1 to 2 at the optimal operating temperature of 100°C to 100 ppm acetone gas, tested every 5 days over a month. Detailed Implementation

[0058] The present invention will now be described in detail with reference to the embodiments.

[0059] Example 1

[0060] A method for preparing a cubic spinel structured sulfide composite gas-sensitive material specifically includes the following steps:

[0061] (1) Dissolve 0.35 mmol FeCl2, 0.15 mmol CdCl2, 1.35 mmol InCl3, 2.5 mmol thiourea and 1 mmol sodium citrate in 15 mL of deionized water and stir magnetically in a 50 mL beaker at 500 rpm for 30 min.

[0062] (2) The solution obtained in step (1) was transferred to a high-pressure reactor with a volume of 25 mL, heated and kept warm in an oven, and hydrothermally reacted at 180 °C for 20 h. After the reaction was completed, it was naturally cooled to room temperature, and then washed three times by centrifugation with a mixed solution of deionized water and anhydrous ethanol. Then it was dried at a constant temperature of 60 °C for 12 h to obtain the red precursor material.

[0063] (3) The red precursor material was placed in a tube furnace and heated to 300°C at a heating rate of 2°C / min. After calcination for 2 hours, it was cooled with the furnace to obtain cubic spinel structure FeIn2S4 / CdIn2S4 heterojunction material powder.

[0064] A method for fabricating a gas sensor based on a cubic spinel structure sulfide composite gas-sensitive material, specifically including the following steps:

[0065] (1) Take an Al2O3 ceramic tube with an inner diameter of 0.7 mm, an outer diameter of 1 mm, and a length of 4.5 mm, and fix it at the center of the hexagonal electrode base. The surface of the ceramic tube is covered with two separate parallel ring-shaped gold electrodes. The width of a single ring-shaped gold electrode is 0.4 mm, and the distance between the two ring-shaped gold electrodes is 0.5 mm. A platinum conductive wire with a length of 5 mm is connected to the upper and lower ends of each gold electrode. The other ends of the four platinum conductive wires are respectively welded to the corresponding four corners of the hexagonal electrode base. The nickel-chromium alloy resistance wire passes through the inside of the ceramic tube, and the two ends of the nickel-chromium alloy resistance wire are respectively welded to the two corners of the hexagonal electrode base opposite to the end face of the ceramic tube.

[0066] (2) Take 50 mg of the cubic spinel FeIn2S4 / CdIn2S4 heterojunction material powder prepared in Example 1, mix it in 80 μL of anhydrous ethanol to form a suspension, use a pipette to take out the prepared suspension and coat it on the surface of the ceramic tube of the sensor in step (1), and make the gold electrode completely covered by the material.

[0067] (3) The sensor obtained in step (2) is aged in an air environment at 150°C for 2 days to obtain a semiconductor gas sensor based on cubic spinel structure sulfide composite gas-sensitive material.

[0068] Example 2

[0069] A method for preparing a cubic spinel structured sulfide composite gas-sensitive material specifically includes the following steps:

[0070] (1) Dissolve 0.45 mmol FeCl2, 0.05 mmol CdCl2, 1 mmol InCl3, 3.5 mmol thiourea and 1.5 mmol citric acid in 15 mL deionized water and stir magnetically in a 50 mL beaker at 450 rpm for 20 min.

[0071] (2) The solution obtained in step (1) was transferred to a high-pressure reactor with a volume of 25 mL, heated and kept warm in an oven, and hydrothermally reacted at 190 °C for 22 h. After the reaction was completed, it was naturally cooled to room temperature, and then washed three times by centrifugation with a mixed solution of deionized water and anhydrous ethanol. Then it was dried at a constant temperature of 40 °C for 18 h to obtain the red precursor material.

[0072] (3) The red precursor material was placed in a tube furnace and heated to 250°C at a heating rate of 3°C / min. After calcination for 1 hour, it was cooled with the furnace to obtain cubic spinel structure FeIn2S4 / CdIn2S4 heterojunction material powder.

[0073] A method for fabricating a gas sensor based on a cubic spinel structure sulfide composite gas-sensitive material, specifically including the following steps:

[0074] (1) Take an Al2O3 ceramic tube with an inner diameter of 0.7 mm, an outer diameter of 1 mm, and a length of 4.5 mm, and fix it at the center of the hexagonal electrode base. The surface of the ceramic tube is covered with two separate parallel ring-shaped gold electrodes. The width of a single ring-shaped gold electrode is 0.4 mm, and the distance between the two ring-shaped gold electrodes is 0.5 mm. A platinum conductive wire with a length of 5 mm is connected to the upper and lower ends of each gold electrode. The other ends of the four platinum conductive wires are respectively welded to the corresponding four corners of the hexagonal electrode base. The nickel-chromium alloy resistance wire passes through the inside of the ceramic tube, and the two ends of the nickel-chromium alloy resistance wire are respectively welded to the two corners of the hexagonal electrode base opposite to the end face of the ceramic tube.

[0075] (2) Take 55 mg of the cubic spinel structure FeIn2S4 / CdIn2S4 heterojunction material powder prepared in Example 2, mix it in 60 μL of anhydrous ethanol to form a suspension, use a pipette to take out the prepared suspension and coat it on the surface of the ceramic tube of the sensor in step (1), and make the gold electrode completely covered by the material.

[0076] (3) The sensor obtained in step (2) is aged in an air environment at 100°C for 3 days to obtain a semiconductor gas sensor based on cubic spinel structure sulfide composite gas-sensitive material.

[0077] Example 3

[0078] A method for preparing a cubic spinel structured sulfide composite gas-sensitive material specifically includes the following steps:

[0079] (1) Dissolve 0.25 mmol FeCl2, 0.25 mmol CdCl2, 1.35 mmol InCl3, 2.5 mmol thiourea and 1 mmol citric acid in 15 mL deionized water and stir magnetically in a 50 mL beaker at a speed of 500 rpm for 30 min.

[0080] (2) The solution obtained in step (1) was transferred to a high-pressure reactor with a volume of 25 mL, heated and kept warm in an oven, and hydrothermally reacted at 180 °C for 20 h. After the reaction was completed, it was naturally cooled to room temperature, and then washed three times by centrifugation with a mixed solution of deionized water and anhydrous ethanol. Then it was dried at a constant temperature of 60 °C for 12 h to obtain the red precursor material.

[0081] (3) The red precursor material was placed in a tube furnace and heated to 300°C at a heating rate of 2°C / min. After calcination for 2 hours, it was cooled with the furnace to obtain cubic spinel structure FeIn2S4 / CdIn2S4 heterojunction material powder.

[0082] A method for fabricating a gas sensor based on a cubic spinel structure sulfide composite gas-sensitive material, specifically including the following steps:

[0083] (1) Take an Al2O3 ceramic tube with an inner diameter of 0.7 mm, an outer diameter of 1 mm, and a length of 4.5 mm, and fix it at the center of the hexagonal electrode base. The surface of the ceramic tube is covered with two separate parallel ring-shaped gold electrodes. The width of a single ring-shaped gold electrode is 0.4 mm, and the distance between the two ring-shaped gold electrodes is 0.5 mm. A platinum conductive wire with a length of 5 mm is connected to the upper and lower ends of each gold electrode. The other ends of the four platinum conductive wires are respectively welded to the corresponding four corners of the hexagonal electrode base. The nickel-chromium alloy resistance wire passes through the inside of the ceramic tube, and the two ends of the nickel-chromium alloy resistance wire are respectively welded to the two corners of the hexagonal electrode base opposite to the end face of the ceramic tube.

[0084] (2) Take 50 mg of the cubic spinel structure FeIn2S4 / CdIn2S4 heterojunction material powder prepared in Example 3, mix it in 80 μL of anhydrous ethanol to form a suspension, use a pipette to take out the prepared suspension and coat it on the surface of the ceramic tube of the sensor in step (1), and make the gold electrode completely covered by the material.

[0085] (3) The sensor obtained in step (2) is aged in an air environment at 150°C for 2 days to obtain a semiconductor gas sensor based on cubic spinel structure sulfide composite gas-sensitive material.

[0086] Example 4

[0087] A method for preparing a cubic spinel structured sulfide composite gas-sensitive material specifically includes the following steps:

[0088] (1) Dissolve 0.15 mmol FeCl2, 0.35 mmol CdCl2, 1.35 mmol InCl3, 2.5 mmol thiourea and 1 mmol citric acid in 15 mL of deionized water and stir magnetically in a 50 mL beaker at 500 rpm for 30 min.

[0089] (2) The solution obtained in step (1) was transferred to a high-pressure reactor with a volume of 25 mL, heated and kept warm in an oven, and hydrothermally reacted at 180 °C for 20 h. After the reaction was completed, it was naturally cooled to room temperature, and then washed three times by centrifugation with a mixed solution of deionized water and anhydrous ethanol. Then it was dried at a constant temperature of 60 °C for 12 h to obtain the red precursor material.

[0090] (3) The red precursor material was placed in a tube furnace and heated to 300°C at a heating rate of 2°C / min. After calcination for 2 hours, it was cooled with the furnace to obtain cubic spinel structure FeIn2S4 / CdIn2S4 heterojunction material powder.

[0091] A method for fabricating a gas sensor based on a cubic spinel structure sulfide composite gas-sensitive material, specifically including the following steps:

[0092] (1) Take an Al2O3 ceramic tube with an inner diameter of 0.7 mm, an outer diameter of 1 mm, and a length of 4.5 mm, and fix it at the center of the hexagonal electrode base. The surface of the ceramic tube is covered with two separate parallel ring-shaped gold electrodes. The width of a single ring-shaped gold electrode is 0.4 mm, and the distance between the two ring-shaped gold electrodes is 0.5 mm. A platinum conductive wire with a length of 5 mm is connected to the upper and lower ends of each gold electrode. The other ends of the four platinum conductive wires are respectively welded to the corresponding four corners of the hexagonal electrode base. The nickel-chromium alloy resistance wire passes through the inside of the ceramic tube, and the two ends of the nickel-chromium alloy resistance wire are respectively welded to the two corners of the hexagonal electrode base opposite to the end face of the ceramic tube.

[0093] (2) Take 50 mg of the cubic spinel FeIn2S4 / CdIn2S4 heterojunction material powder prepared in Example 4, mix it in 80 μL of anhydrous ethanol to form a suspension, use a pipette to take out the prepared suspension and coat it on the surface of the ceramic tube of the sensor in step (1), and make the gold electrode completely covered by the material.

[0094] (3) The sensor obtained in step (2) is aged in an air environment at 150°C for 2 days to obtain a semiconductor gas sensor based on cubic spinel structure sulfide composite gas-sensitive material.

[0095] Example 5

[0096] A method for preparing a cubic spinel structured sulfide composite gas-sensitive material specifically includes the following steps:

[0097] (1) Dissolve 0.05 mmol FeCl2, 0.45 mmol CdCl2, 1.25 mmol InCl3, 5 mmol thiourea and 2 mmol citric acid in 15 mL deionized water and stir magnetically in a 50 mL beaker at a speed of 550 rpm for 40 min.

[0098] (2) The solution obtained in step (1) was transferred to a high-pressure reactor with a volume of 25 mL, heated and kept warm in an oven, and hydrothermally reacted at 200 °C for 24 h. After the reaction was completed, it was naturally cooled to room temperature, and then washed three times by centrifugation with a mixed solution of deionized water and anhydrous ethanol. It was then dried at a constant temperature of 50 °C for 24 h to obtain the red precursor material.

[0099] (3) The red precursor material was placed in a tube furnace and heated to 350°C at a heating rate of 4°C / min. After calcination for 3 hours, it was cooled with the furnace to obtain cubic spinel structure FeIn2S4 / CdIn2S4 heterojunction material powder.

[0100] A method for fabricating a gas sensor based on a cubic spinel structure sulfide composite gas-sensitive material, specifically including the following steps:

[0101] (1) Take an Al2O3 ceramic tube with an inner diameter of 0.7 mm, an outer diameter of 1 mm, and a length of 4.5 mm, and fix it at the center of the hexagonal electrode base. The surface of the ceramic tube is covered with two separate parallel ring-shaped gold electrodes. The width of a single ring-shaped gold electrode is 0.4 mm, and the distance between the two ring-shaped gold electrodes is 0.5 mm. A platinum conductive wire with a length of 5 mm is connected to the upper and lower ends of each gold electrode. The other ends of the four platinum conductive wires are respectively welded to the corresponding four corners of the hexagonal electrode base. The nickel-chromium alloy resistance wire passes through the inside of the ceramic tube, and the two ends of the nickel-chromium alloy resistance wire are respectively welded to the two corners of the hexagonal electrode base opposite to the end face of the ceramic tube.

[0102] (2) Take 60 mg of the cubic spinel structure FeIn2S4 / CdIn2S4 heterojunction material powder prepared in Example 5, mix it in 70 μL of anhydrous ethanol to form a suspension, use a pipette to take out the prepared suspension and coat it on the surface of the ceramic tube of the sensor in step (1), and make the gold electrode completely covered by the material.

[0103] (3) The sensor obtained in step (2) is aged in an air environment at 200°C for 4 days to obtain a semiconductor gas sensor based on a cubic spinel structure sulfide composite gas-sensitive material.

[0104] Comparative Example 1

[0105] A method for fabricating a semiconductor acetone gas sensor based on FeIn2S4 material, specifically including the following steps:

[0106] (1) Dissolve 0.5 mmol FeCl2, 1.35 mmol InCl3, 3.5 mmol thiourea and 1.5 mmol citric acid in 15 mL deionized water and stir magnetically in a 50 mL beaker at a speed of 450 rpm for 30 min.

[0107] (2) The solution obtained in step (1) was transferred to a high-pressure reactor with a volume of 25 mL. The hydrothermal reaction was carried out in an oven at 190 °C for 22 h. After naturally cooling to room temperature, the solution was washed three times by centrifugation with a mixed solution of deionized water and anhydrous ethanol. Then it was dried at a constant temperature of 40 °C for 18 h.

[0108] (3) The red precursor material from step (2) was placed in a tube furnace and heated to 250°C at a heating rate of 3°C / min and calcined for 1 hour to obtain spinel structure FeIn2S4 material powder, which was labeled as FeIn2S4.

[0109] (4) Take an Al2O3 ceramic tube with an inner diameter of 0.7 mm, an outer diameter of 1 mm, and a length of 4.5 mm, and fix it at the center of the hexagonal electrode base. Cover the surface of the ceramic tube with two separate parallel ring-shaped gold electrodes. The width of a single ring-shaped gold electrode is 0.4 mm, and the distance between the two ring-shaped gold electrodes is 0.5 mm. Connect a 5 mm long platinum conductive wire to the upper and lower ends of each gold electrode. The other ends of the four platinum conductive wires are respectively welded to the corresponding four corners of the hexagonal electrode base. The nickel-chromium alloy resistance wire passes through the inside of the ceramic tube, and the two ends of the nickel-chromium alloy resistance wire are respectively welded to the two corners of the hexagonal electrode base opposite to the end face of the ceramic tube.

[0110] (5) Take 55mg of the material powder obtained in step (3) and mix it with 60μL of anhydrous ethanol to form a suspension. Use a pipette to take out the prepared suspension and apply it to the surface of the ceramic tube of the sensor prepared in step (4) so ​​that the gold electrode is completely covered by the material.

[0111] (6) The prepared sensor was aged in an air environment at 100°C for 3 days to obtain a semiconductor acetone gas sensor based on FeIn2S4 material.

[0112] Comparative Example 2

[0113] A method for fabricating a semiconductor acetone gas sensor based on CdIn2S4 material, specifically including the following steps:

[0114] (1) Dissolve 0.5 mmol of CdCl2, 1.25 mmol of InCl3, 5 mmol of thiourea and 2 mmol of sodium citrate in 15 mL of deionized water and stir magnetically in a 50 mL beaker at a speed of 550 rpm for 30 min.

[0115] (2) Transfer the solution obtained in step (1) to a high-pressure reactor with a volume of 25 mL, and carry out hydrothermal reaction in an oven at 200 °C for 24 h. After naturally cooling to room temperature, wash three times with a mixed solution of deionized water and anhydrous ethanol, and then dry at a constant temperature of 50 °C for 24 h.

[0116] (3) The red precursor material from step (2) was placed in a tube furnace and heated to 350°C at a heating rate of 4°C / min and calcined for 3 hours to obtain spinel-structured CdIn2S4 material powder, which was labeled as CdIn2S4.

[0117] (4) Take an Al2O3 ceramic tube with an inner diameter of 0.7 mm, an outer diameter of 1 mm, and a length of 4.5 mm, and fix it at the center of the hexagonal electrode base. Cover the surface of the ceramic tube with two separate parallel ring-shaped gold electrodes. The width of a single ring-shaped gold electrode is 0.4 mm, and the distance between the two ring-shaped gold electrodes is 0.5 mm. Connect a 5 mm long platinum conductive wire to the upper and lower ends of each gold electrode. The other ends of the four platinum conductive wires are respectively welded to the corresponding four corners of the hexagonal electrode base. The nickel-chromium alloy resistance wire passes through the inside of the ceramic tube, and the two ends of the nickel-chromium alloy resistance wire are respectively welded to the two corners of the hexagonal electrode base opposite to the end face of the ceramic tube.

[0118] (5) Take 60mg of the material powder obtained in step (3) and mix it with 70μL of anhydrous ethanol to form a suspension. Use a pipette to take out the prepared suspension and apply it to the surface of the ceramic tube of the sensor prepared in step (4) so ​​that the gold electrode is completely covered by the material.

[0119] (6) The prepared sensor was aged in an air environment at 200°C for 4 days to obtain a semiconductor acetone gas sensor based on FeIn2S4 material.

[0120] Performance testing:

[0121] XRD tests were performed on the cubic spinel FeIn2S4 / CdIn2S4 heterojunction materials prepared in Examples 1 to 5, the FeIn2S4 material of Comparative Example 1, and the CdIn2S4 material of Comparative Example 2. Figure 1 As shown, since FeIn2S4 and CdIn2S4 have similar characteristic peaks and crystal structures, the diffraction peaks of the heterojunction materials prepared in Examples 1 to 5 are different from those of Comparative Example 1 and Comparative Example 2 only in terms of offset angle and diffraction peak intensity.

[0122] SEM tests were performed on the cubic spinel FeIn2S4 / CdIn2S4 heterojunction materials prepared in Examples 1 to 5, the FeIn2S4 material of Comparative Example 1, and the CdIn2S4 material of Comparative Example 2. Figures 2 to 8 As shown, the gas-sensitive materials prepared in Examples 1 to 5 and Comparative Examples 1 to 2 are all spherical structures. Although the nanospheres formed by FeIn2S4, FeIn2S4 / CdIn2S4 and CdIn2S4 are slightly different in size and shape, it shows that the present invention can successfully synthesize spherical composite structure sulfide nanomaterials.

[0123] The semiconductor gas sensors of Examples 1 to 5 and Comparative Examples 1 to 2 were tested for their response to 100 ppm acetone gas at temperatures ranging from 70°C to 120°C. Figure 9As shown, the sensor sensitivity within this temperature range first increases and then decreases with increasing temperature, indicating that 100℃ is the optimal operating temperature. Furthermore, all embodiments exhibit better sensing performance than Comparative Example 1 and Comparative Example 2, demonstrating that the synthesized CdIn2S4 / FeIn2S4 heterojunction material can effectively improve the acetone sensing effect.

[0124] The detection range of the semiconductor gas sensors of Examples 1 to 5 and Comparative Examples 1 to 2 was tested, such as... Figures 10 to 14 As shown, the semiconductor gas sensors of various embodiments of the present invention exhibit increased response to different concentrations of acetone gas at 100°C with increasing concentration, while maintaining both a low lower detection limit and a high upper detection limit. Figures 15-16 As shown, Comparative Examples 1 and 2 have lower detection limits, while the embodiments of the present invention have a wider detection range.

[0125] Periodic tests were performed on the semiconductor gas sensors of Examples 1 to 5 and Comparative Examples 1 to 2, such as... Figures 17 to 23 As shown, after multiple cycles of testing with 100ppm acetone gas at an operating temperature of 100℃, the semiconductor gas sensors of the various embodiments of the present invention exhibit good repeatability, which is superior to Comparative Example 1 and Comparative Example 2.

[0126] Stability tests were performed on the semiconductor gas sensors of Examples 1 to 5 and Comparative Examples 1 to 2, such as... Figure 24 As shown, the semiconductor gas sensors of Examples 1 to 5 and Comparative Examples 1 to 2 were continuously tested for 100 ppm acetone gas at an operating temperature of 100°C for one month, with the response value tested every 5 days. It can be seen that the responses of the embodiments of the present invention are significantly better than those of Comparative Examples 1 and 2, and the response values ​​change less, showing good stability.

Claims

1. A method for preparing a cubic spinel-structured sulfide composite gas-sensitive material, characterized in that, Using FeCl2, CdCl2, and InCl3 as metal sources and thiourea as a sulfur source, they are placed together in a solvent of water, with citric acid or sodium citrate added as a dispersant. A precursor material is obtained through a hydrothermal reaction, followed by calcination and annealing to obtain a cubic spinel structure FeIn2S4 / CdIn2S4 heterojunction material powder. The specific steps include: (1) Dissolve FeCl2, CdCl2, InCl3, thiourea and dispersant in water at a molar ratio of (0.05-0.45):(0.05-0.45):(1-1.35):(2.5-5):(1-2), stir to dissolve, and obtain a solution; (2) Transfer the solution obtained in step (1) to a high-pressure reactor and heat it to the hydrothermal reaction temperature of 180℃-200℃. The hydrothermal reaction is carried out for 20h-24h. After the reaction is completed, it is naturally cooled to room temperature. After washing, it is dried at a constant temperature of 40℃-60℃ for 12h-24h to obtain the red precursor material. (3) The red precursor material is placed in a heating furnace and heated to a calcination temperature of 250℃-350℃ at a heating rate of 2℃ / min-4℃ / min. The material is calcined for 1h-3h and then cooled to room temperature with the furnace to obtain cubic spinel structure FeIn2S4 / CdIn2S4 heterojunction material powder.

2. The preparation method of a cubic spinel structure sulfide composite gas-sensitive material as described in claim 1, characterized in that, In step (1), magnetic stirring is used with a rotor speed of 450 rpm to 550 rpm for 20 min to 40 min.

3. A cubic spinel-structured sulfide composite gas-sensitive material, characterized in that, The gas-sensitive material is prepared using the method described in claim 1 or 2 for preparing cubic spinel structure sulfide composite gas-sensitive materials.

4. A gas sensor based on a cubic spinel structure sulfide composite gas-sensitive material, employing a side-heated structure, comprising two parallel annular gold electrodes, a ceramic tube, a conductive wire, a heating resistance wire, and an electrode base, characterized in that... The two gold electrodes and the ceramic tube are coated with the cubic spinel structure sulfide composite gas-sensitive material as described in claim 3.

5. A method for preparing a gas sensor based on a cubic spinel structure sulfide composite gas-sensitive material as described in claim 4, characterized in that, Specifically, the following steps are included: (1) Take an Al2O3 ceramic tube and fix it at the center of the hexagonal electrode base. The surface of the Al2O3 ceramic tube is covered with two discrete parallel gold electrodes. Each gold electrode is connected to a platinum conductive wire at both ends. The other ends of the four platinum conductive wires are connected to the four electrodes corresponding to the hexagonal electrode base. The nickel-chromium alloy resistance wire passes through the inside of the ceramic tube. The two ends of the nickel-chromium alloy resistance wire are connected to the two electrodes of the hexagonal electrode base opposite to the end face of the ceramic tube. (2) The cubic spinel structure FeIn2S4 / CdIn2S4 heterojunction material powder is added to anhydrous ethanol to form a suspension, and the ceramic tube surface and gold electrode of step (1) are coated to make the gold electrode completely covered by the suspension. (3) The sensor obtained in step (2) is subjected to heating and aging treatment to obtain a semiconductor gas sensor based on cubic spinel structure sulfide composite gas-sensitive material.

6. The method for preparing a gas sensor based on a cubic spinel structure sulfide composite gas-sensitive material as described in claim 5, characterized in that, Step (1) The inner diameter of the Al2O3 ceramic tube is 0.6mm-0.8mm, the outer diameter is 1.0mm-1.3mm, and the length is 4.0mm-5.0mm; The width of each ring-shaped gold electrode is 0.4mm-0.5mm, and the spacing between two ring-shaped gold electrodes is 0.5mm-0.6mm; The length of each platinum conductive wire is 4mm-5mm; Step (2) The mass-to-volume ratio of cubic spinel FeIn2S4 / CdIn2S4 heterojunction material powder to anhydrous ethanol is (50-60) mg:(60-80) μL; Step (3) The temperature for heating and aging is 100℃-200℃, and the aging time is 2-4 days.

7. An application of the gas sensor based on the cubic spinel structure sulfide composite gas-sensitive material as described in claim 4, characterized in that, For accurate monitoring of trace amounts of acetone gas at relatively low temperatures up to 100°C.

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